A new wave of digital works has collectors bidding

Rafaël Rozendaal, a 33-year-old New Yorker with Internet tattooed on his inner lip, has a knack for turning screensavers into art. As the online king of digital art, he builds interactive websites that draw as many as 40 million viewers a year. And unlike a gallery with paintings or sculpture, his websites allow you to play with works like ifnoyes.com changing the way they look by moving your cursor across the screen. Visiting the site is free, but the auction house Phillips is certain that cutting-edge collectors are ready to shell out as much as $6,000 for the right...